Low IQ Linked to Type of Dementia

The most common type of dementia after Alzheimer's disease, vascular dementia occurs when blood flow to the brain is impaired.

The study examined 173 people in Scotland who took a test of their mental ability in 1932 when they were about eleven years old and later developed dementia. This group was compared to one set of control participants of the same age and gender. For another group of controls, the researchers made sure that the cases and controls came from families where the fathers had similar types of occupations.

The people with vascular dementia were 40 percent more likely to have low test scores when they were children than the people who did not develop dementia. This difference was not true for those with Alzheimer's disease.

"These results point to the importance of reducing the vascular risk factors that can lead to strokes and dementia," said study author John M. Starr, FRCPEd, of the University of Edinburgh. "Risk factors include high blood pressure, high cholesterol and smoking."

Starr said the findings support the hypothesis that low childhood IQ acts as a risk factor for dementia through vascular risks rather than the "cognitive reserve" theory. This theory speculates that greater IQ and education create a buffer against the effects of dementia in the brain, allowing people with greater cognitive reserve to stay free of signs of dementia longer, even though the disease has started affecting their brains.